Answer: The subject of a work of art is A. what is being represented in the piece.
Step-by-step explanation: In a work of art, the subject is the central idea that is being depicted. Some people define the subject as the essence of the work of art as the subject is directly linked to what the artist intends to express and wants to show to the audience. Popular subjects in a work of art are love, death and nature. Taking this into consideration, it can be said that option A. is the one that answers the question "what is the subject?".